Structure of power transmission apparatus

Abstract

A power transmission system transmits power from a drive shaft of an internal combustion engine to a first and a second auxiliary device through a belt. An auto-tensioner extends or contracts to change the tension of the belt. A controller rotates the first auxiliary device in a reverse direction to loosen the belt to cause the auto-tensioner to extend to increase the tension of the belt and calculates a reversing timing when the drive shaft will be reversed as a result of increasing of the tension of the belt. The controller inhibits the tensioner body from contracting immediately before or when the reversing time is reached to keep the tension of the belt at an increased degree, thereby eliminating the slippage of the belt on each pulley without having to finely control the operation of the first auxiliary device when the internal combustion engine is started.

Description

CROSS REFERENCE TO RELATED DOCUMENT[0001]The present application claims the benefit of priority of Japanese Patent Application No. 2013-259996 filed on Dec. 17, 2013, the disclosure of which is incorporated herein by reference.BACKGROUND OF THE INVENTION[0002]1. Technical Field[0003]This disclosure relates generally to a power transmission apparatus designed to transmit power, as produced by an internal combustion engine, to auxiliary devices.[0004]2. Background Art[0005]There are known power transmission systems which work to transmit output power of an internal combustion engine to a given accessory and other accessories mounted in, for example, an automobile using an endless transmitting member such as a belt. The given accessory is used as, for instance, an engine starter to start the internal combustion engine. The given accessory may be rotated by the output power of the internal combustion engine along with the other accessories in a regenerative mode of operation to generate...

AI Technical Summary

Benefits of technology

[0011]It is therefore an object to provide an improved structure of a power transmission system designed to minimize slippage of an endless transmitting member on a pulley without having to finely control an operation of an auxiliary device when it is required to start an internal combustion engine.

[0012]According to one aspect of the invention, there is provided a power transmission system which works to transmit power, as produced by an internal combustion engine, to a first auxiliary device and a second auxiliary device. The first auxiliary device is operable either in a motor mode or in a regenerative mode. The power transmission system comprises: (a) a driving pulley which is joined to a drive shaft of the internal combustion engine to be rotatable along with rotation of the drive shaft; (b) a first auxiliary device pulley which is joined to a shaft of the first auxiliary device to be rotatable along with rotation of the shaft of the first auxiliary device; (c) a second auxiliary device pulley which is joined to a shaft of the second auxiliary device to be rotatable along with rotation of the shaft of the second auxiliary device; (d) an endless transmitting member which is wound around the driving pulley, the first auxiliary device pulley, and the second auxiliary device pulley; (e) a tensioner pulley which is rotatable in contact with the endless transmitting member, the tensioner pulley being also movable relative to the internal combustion engine; (f) an auto-tensioner which is equipped with a tensioner body, the tensioner body working to extend or contract in a given direction to move the tensioner pulley relative to the internal combustion engine, thereby changing a degree of tension of the endless transmitting member; (g) a biasing mechanism which biases the tensioner body to extend in the given direction; and (h) a stroke inhibitor which works to inhibit the tensioner body from contracting. The auto-tensioner may work to eliminate slippage of the endless transmitting member between the driving pulley and the first auxiliary device pulley or between the driving pulley and the second auxiliary device pulley when the first auxiliary device operates in the regenerative mode.

[0014]Specifically, the controller controls the operation of the first auxiliary device so as to extend the tensioner body in the given direction for increasing the tension of the endless transmitting member in the reverse rotation control mode. This keeps the tension of the endless transmitting member increased when it is required to start the first auxiliary device to operate in the motor mode in the engine start mode, thereby minimizing the slippage of the endless transmitting member on each of the first and second auxiliary device pulleys when the internal combustion engine is cranked.

[0015]After the internal combustion engine starts, the controller enters the inhibition releasing mode to cause the tensioner body to contract, thereby decreasing the tension of the endless transmitting member which has been increased by reverse rotation of the first auxiliary device in the reverse rotation control mode. This avoids an undesirable increase in frictional resistance of the endless transmitting member on each of the first and second auxiliary device pulleys and minimizes the wear or damage to the endless transmitting member.

[0016]The controller, as already described, works to predict the reversing timing when the drive shaft (i.e., the internal combustion engine) will start being reversed and control the operation of the first auxiliary device based on the reversing timing in the reverse rotation control mode. Specifically, the controller stops the reverse rotation of the first auxiliary device immediately before or at the moment when the reversing timing is reached, thereby keeping the tensioner body at a desired extended position without causing the drive shaft to rotate in the reverse direction. This eliminates the need for finely controlling the operation of the first auxiliary device to output a degree of torque within a range which is higher than that permitting the tensioner body to extend in the given direction thereof and is lower than that causing the drive shaft to rotate in the reverse direction. The power transmission system is, therefore, capable of controlling the slippage of the endless transmitting member on each of the first and second auxiliary device pulleys without having to finely control the operation of the first auxiliary device when the internal combustion engine is started.

Problems solved by technology

When the above torque range is narrow, it results in a difficulty in keeping the output, as produced by the given accessory, within the torque range at all times.

When the torque, as produced by the given accessory which reverses in the reverse rotation control step, is lower than that causing the tensioner body to extend in the given direction, it will result in a difficulty in increasing the tension of the endless transmitting member to a required degree, which may lead to the slippage of the endless transmitting member on each of the pulleys.

Images